At purification of water different types of aqueous solutions of metal salts, such as aluminum sulphate, aluminum chloride, ferri chloride, and the similar are used. The basic polysalts of aluminum chloride and aluminum sulphate or mixed aluminum-ferri chloride are in this case particularly effective and of interest. Common to all processes for the manufacture of such solutions are that they all require high temperatures and concentrated acids in order to have the dissolution and reaction with the minerals, which are the source of the metal salts, to run with a reasonable speed. Due to these process parameters all equipment has to be made of corrosion resistant materials, as well as the equipment materials shall all be able to resist high pressures in those cases an elevated pressure is used to speed up the process.
Further the process capacity of the plants is limited due to the fact that the reaction time is long, two hours being the shortest time, and is hereby due for the more simple products, such as aluminum sulphate and aluminnum chloride. More advanced products, such as the basic salt solutions require a longer time and e.g., polyaluminum chloride-sulphate requires 6 hrs at 160.degree. C. to be produced.
There is thus a well grounded demand for obtaining better processes which can increase and cost-reduce the production of such aluminum and ferri salt solutions, in particular since the world community today requires increased water purification of economically weak nations and communities as well.